The present invention relates to a device for controlling steering signals for a radio-controlled model helicopter.
Helicopters can make a flight by rotating the main rotor, with the wings (blades) thereof adjusted to a certain attack angle, thus producing a lift. The steering is performed to four-axis control directions including roll, pitch, collective pitch, and yaw. The roll axis, the pitch axis, the collective axis, and the yaw axis are controlled by adjusting the rotor pitch angle of the rotating plane of the main rotor of a helicopter. For this control, a swash plate, which is disposed coaxially on the rotating shaft of the main rotor and of which the three axes have the degree of freedom, is controlled by means of servomechanisms.
FIG. 5 shows the principle of the control (here, the main rotor is not shown). The forward and backward control, shown in FIG. 5(a), is called pitch control (often referred to as elevator control). The rightward and leftward control, shown in FIG. 5(b), is called roll control (referred to as aileron control). The ascent and descent control, shown in FIG. 5(c), is called collective pitch control. In flight, the helicopter can travel in a desired direction by combining the above-mentioned controls.
In order to fly the body forward (in the direction of the arrow A), shown in FIG. 5(a), the servomechanism (not shown) controls the swash plate 12 disposed coaxially on the rotating shaft 11 of the main rotor to tilt the body in the direction of the arrow (a). In order to advance the body backward, the swash plate 12 is tilt in the reverse direction. The swash plate 12 is tilted in the opposite direction to fly the body backward.
In order to fly the body leftward (in the direction of the arrow B), shown in FIG. 5(b), the servomechanism (not shown) controls the swash plate 12 to tilt the body in the direction of the arrow (b).
In order to fly the body upward (in the direction of the arrow C), shown in FIG. 5(c), the servomechanism (not shown) controls the swash plate 12 to tilt the body in the direction of the arrow (c).
In the conventional roll, pitch, and corrective pitch steering method for the model helicopter steering device, independent mechanisms control the swash plate. However, recently, the so-called swash mixing method where three steering elements are mixed to steer a helicopter has been broadly used.
FIG. 6 is a cross-sectional view illustrating the swash plate 12 called a 120xc2x0 swash plate. FIG. 7 is a perspective view illustrating the swash plate 12 called a 120xc2x0 swash plate.
The swash plate 12, which controls the main rotor (not shown), is formed of a lower plate 13a and an upper plate 13b. The plates 13a and 13b are tiltably mounted on the rotating shaft 11. The lower plate 13a can be vertically slid on the rotating shaft 11 of the main rotor 11a and does not depend on the rotation of the rotor 11. The upper plate 13b, which rotates in harmony with the rotating shaft 11, is mounted coaxially together with the rotating axis 11 and the lower plate 13a.
The main control rods 16a, 16b, 16c, and 16d are faced oppositely to and linked perpendicularly to each other on the circumference of the upper plate 13b. The other end of each rod extends to the main rotor 11a. The swash plate control rods 15a, 15b, and 15c are linked on the outer circumference of the lower plate 13a at intervals of 120xc2x0. The pitch servomechanism 14a, the collective pitch servomechanism 14b, and the roll servomechanism 14c are directly linked to the other ends of the swash plate control rods 15a, 15b, and 15c, respectively. Moreover, the control device is prepared that cooperatively operates the three servomechanisms in accordance with a collective pitch control amount and cooperatively operates the three servomechanisms in accordance with a roll control amount or pitch control amount. The control device selectively operates cooperatively the three servomechanisms through the electrical mixing process.
In the roll manipulation, for example, the right and left direction control of the body is performed as follows. That is, the collective pitch servomechanism 14b is moved by the same amount in the direction opposite to the moving direction of the roll servomechanism 14c. The swash plate control rods 15b and 15c are vertically moved to rotate on the axes (Y, Y) (FIG. 6) as center. Thus, the lower plate 13a and the upper plate 13b are tilted. By controlling the main control rods 16a to 16d, the pitch angle of a blade of the main rotor 11a is changed.
In the pitch manipulation, the operation amount is controlled to xc2xd in the direction opposite to the movement of the pitch servomechanism 14a to operate the roll servomechanism 14c and the collective pitch servomechanism 14b. The swash plate control rods 15a to 15c are vertically moved to rotate on the axes (X, X) (FIG. 6) as center. Thus, the lower plate 13a and the upper plate 13b are tilted and the main control rods 16a to 16d are controlled. The pitch angle of the blade of the main rotor 11a is changed so that the forward and backward movements of the body are controlled.
In the collective pitch manipulation, all the three servomechanisms 14a to 14c are controlled in a similar manner to operate vertically. Thus, the swash plate control rods 15a to 15c are traveled vertically by the same amount. The lower plate 13a and the upper plate 13b are vertically moved in parallel on the circumference of the driving shaft 11, with the plates 13a and 13b maintained to the original tilt. Thus, when the main control rods 16a to 16d move vertically, the pitch angle of the blade of the main rotor 11a changes. As a result, the upward and downward movement of the body is controlled. 11a is controlled in accordance with the collective pitch control amount. In the roll control, the right and left tilt angles of the main rotor are changed in accordance with the roll control amount. In the pitch control, the front and back tilt angles of the main rotor are changed in accordance with the pitch control amount.
As described above, the plural mixing manipulations allow the swash plate 12 to be controlled.
The direct swash control has the advantage in which the looseness is small because the mechanism is simple and the mechanical linkage allows direct connection to the servomechanism.
However, the direct swash control requires that two or more servomechanisms operate for each axis manipulation. This complicates the control method. The following problems to be solved occur to subject the operation of the servomechanism to the mixing control.
Firstly, since the servo control signals transmitted from the transmitter is converted into a serial pulse sequence, time shifts occur when the servo control signals respectively reach the servomechanisms at the body of a helicopter. This causes a response difference in the servo operation for each axis, thus resulting in an axial interference.
Secondary, when there is a difference between servo operation velocities of the axes, the axial interference occurs in manipulation.
Thirdly, in the pitch control, the roll servomechanism and the collective pitch servomechanism can move by xc2xd of the moving angle of the pitch servomechanism. This operation causes the time difference between servo operations, thus resulting in an axial interference.
Finally, the servomechanism generally moves circularly to implement the control operation. For control, pivots, arranged in a disk pattern, are linked to the pivots of the swash plate. The collective pitch manipulation causes three servomechanisms to move at the same time, thus offsetting the pivot points. If the roll or pitch manipulation is carried out at the offset point, a difference occurs between the movement of the swash plate in the ascent direction and the movement of the swash plate in the descent direction. As a result, an axial interference occurs in the collective pitch direction.
The present invention is made to solve the above-mentioned problems.
Moreover, the objective of the invention is to provide a steering control device that corrects each servo control signal to minimize the other axis interference produced mechanically by the direct swash controller.
The objective of the present invention is achieved by a steering control device suitable for a radio-controlled model helicopter, comprising a receiver for receiving three steering signals serially transmitted from a transmitter and demodulating, and then outputting three servo control signals, the three steering signals including a roll steering signal, a pitch steering signal, and a collective pitch steering signal, the three servo control signals including a roll servo control signal, a pitch servo control signal, and a collective pitch servo control signal; a controller for mixing as manipulation signals for three axes the three servo control signals output from the receiver and then outputting three servo drive signals for three axes, the three servo drive signals including a roll servo drive signal, a pitch servo drive signal and a collective pitch servo drive signal; a synchronous circuit for synchronizing the three servo drive signals output from the controller and outputting the three servo drive signals in parallel; and a roll servo mechanism, a pitch servo mechanism, and a collective pitch servo mechanism, which are controllably driven respectively by the three servo drive signals.
The steering control device further comprises control amount adjustment computation circuits for computing the three servo control signals respectively as three control amounts for the three axes. The steering control device further comprises time constant circuits for respectively adjusting the operation times of the three servo mechanisms in accordance with said steering signals for three axes from the control amount adjustment computation circuits, which respectively receives the pitch servo control signal. The steering control device further comprises offset correction circuits for respectively correcting offset amounts at servo positions of the three servo mechanisms, in accordance with three steering signals for three axes from the control amount adjustment computation circuits, which respectively receives a roll servo control signal and a pitch servo control signal.